[Clinical value of trastuzumab in the treatment of lapatinib-resistant HER2-positive metastatic breast cancer].

Retrospective and prospective studies have shown that continuous administration of trastuzumab with different chemotherapy regimens resulted in better clinical outcomes than the administration of chemotherapy alone in women with HER2-positive, trastuzumab-refractory metastatic breast cancer (MBC). However, there are limited data to evaluate the activity of trastuzumab in patients progressed after other anti-HER2 therapies, e.g. lapatinib. The aim of the present study was to evaluate retrospectively the clinical value of trastuzumab in patients with lapatinib-resistant HER2-positive advanced breast cancer treated in our center. Patients with HER2-positive MBC who experienced progression after first-line lapatinib-based regimens were assigned to receive either conventional treatment without trastuzumab or in combination with trastuzumab as second-line therapy. The efficacy end points included progression-free survival (PFS) and overall survival (OS). Thirty-five eligible patients progressed after treatment with lapatinib-based regimens were collected. None of the patients had received prior trastuzumab in either the adjuvant or metastatic setting. Twenty-two patients were assigned to receive conventional treatment without trastuzumab as second-line therapy (non-T arm) and 13 patients received conventional treatment combined with trastuzumab (T arm). There were no significant differences in the main clinical factors between the two arms, such as age, PS status, ER/PR, metastatic status, etc. Both the two cases with no disease progression after the second-line therapy were trastuzumab-treated patients, and all the other 33 cases were patients with progression despite the second-line therapy. Twenty-seven patients died due to disease progression, and eight survived (six cases of the T-arm and two cases of the non-T arm). The median PFS was 3.3 months in the non-T arm and 10.0 months in the T arm (P = 0.001). The median OS was 7.0 months in the non-T arm and 31.1 months in the T arm (P = 0.015). Trastuzumab plus conventional treatment is superior to conventional treatment in women with lapatinib-resistant HER2-positive metastatic breast cancer. Continuous anti-HER2 management can provide survival benefit to patients with HER2-positive breast cancer.